Diagnosis: locomotive amoebae usually polypodial, like a dead tree with thick truncate branches; in rapid locomotion monopodial, large, commonly between 600 and 1500 µm long, but up to 5000 µm; pseudopodia usually with ridges; uroid morulate; multinucleate, with up to 1000 or more nuclei; nuclei spherical, biconvex or ellipsoidal discs, with granular nucleolar material; cytoplasm with crystals, often bipyramidal.

Ecology: fresh water, ponds and rivers, especially in floating debris in early spring. Not rare.

Remarks: the only lightmicroscopical difference between Amoeba and Chaos is the number of nuclei. Lightmicroscopically the cytoplasm of Amoeba proteus looks identical with that of Chaos carolinense (Andresen, 1956). I have collected populations of Chaos with both multinucleate and uninucleate specimens!

I have sampled and observed a large number of Chaos-specimens in the Netherlands (several wide spread locations), Sweden (Mörrum-river) and England (Cambridge, pond). All these amoebae had, even within a population, spherical, discoid or convex shaped nuclei, varying in size from 9.6-48.0 µm.

Most measurements in literature come from cultures. Chaos carolinense has been cultured for decennia all over the world. The culture of Chaos illinoisense became extinct after 18 years, but this species was recently rediscovered in North-West Russia. In fact we don’t know much of these large amoebae, though they aren’t very rare, but who is looking for them?

Though a key to the species seems to be a handy instrument for the beginner, for an experienced worker it is a source of doubt, a minefield. Look at the description of the species below.